High speed impact printer logic system



United States Patent 3,453,954 HIGH SPEED IMPACT PRINTER LOGIC SYSTEMRichard A. Pandolfi, Smithtown, N.Y., assignor to Potter InstrumentCompany, Inc., Plaiuview, N.Y., a corporation of New York Filed Sept.21, 1967, Ser. No. 669,540 Int. Cl. G06k 15/02 US. Cl. 10193 4 ClaimsABSTRACT OF THE DISCLOSURE This invention is a simplified logic systemfor a high speed chain printer in which the columns are printed one at atime. The chain circulates in a direction opposite to the direction inwhich the columns are printed while an incremental encoder produces anoutput pulse each time a type font moves past a hammer. These pulses arecounted and compared to the input data. Each time a column is printed,an extra pulse is coupled to the counter in order to account for thefact that a particular character arrives in printing position one countearlier for each successive column.

Background of the invention This invention relates to a high speedimpact printer and, more particularly, to a simplified logic system fora high speed impact chain printer that prints one column at a time.

Conveniently, in high speed chain printers, an incremental shaftposition encoder is used for determining the position of the type fontwith respect to the print hammers. The encoder typically provides onepulse for each character of the font so that in one complete circulationof the font past the print line the encoder provides as many pulses ascharacters (i.e., 64 characters, 64 pulses). A binary counter countsthese pulses and its output is compared with the input from a datasource. When the output of the counter coincides with input data (whichis encoded as a binary number), an output from the comparator causes aselected hammer to fire.

The position of the characters is synchronized usually with the firsthammer, and a reset signal is generated at the end of each completecirculation to reset the counter. A count of one (1) may, therefore,indicate that the letter A is in printing position opposite the firsthammer; a count of two (2), that the letter B is in printing positionopposite this same first hammer and so on. However, owing to the factthat in a chain printer the character font advances along a lineparallel to the print hammers, the same count does not indicate the sameletter is in position with respect to the second and successive hammers.

Several logic systems have been proposed in the prior art for chainprinters to account for the fact that with an incremental encoder aparticular count indicates a particular character only with respect to asingle column. Such prior art systems, while generally satisfactory, arerelatively complex and expensive.

The logic of this invention is the provision of a logic system forcharacter at a time chain printers which simply and inexpensivelycorrelate an incremental encoder output with the column being printed.

Summary of the invention Briefly, this invention contemplates :a chainprinter in which the chain circulates in a direction opposite to that inwhich the columns are printed, and a logic system utilizing anincremental encoder and a counter which cycles at a count equal to thenumber of characters of the font. One additional pulse is coupled to thecounter each time 3,453,954 Patented July 8, 1969 ice a hammer fires andthe counter is not reset until a complete line has been printed. In thissimple manner, the count in the character position code counter advancesso that a particular character is in printing position for eachsuccessively selected hammer.

Brief description of the drawings Having briefly described thisinvention, it will be described in greater detail along with otherobjects and advantages in the following detailed description of apreferred embodiment which may be best understood by reference in theaccompanying drawing which forms a part of the instant specification andwhich is to be read in conjunction therewith and in which the solefigure is a block diagram of a chain printer employing one embodiment ofthe simplified logic system of this invention.

Description of the preferred embodiments Referring now to the drawing, amotor 10 drives a print chain or belt 12 horizontally from right to left(in the direction of the arrow) past a line of solenoid actuated printhammers 14 in a manner known to those skilled in the art. See, forexample, the copending application Ser. No. 509,501, filed Nov. 24, 1965and assigned to the same assignee as this invention.

An incremental encoder is synchronously driven with the chain 12; it maycomprise a metallic disc 16 with a number of slots equal in number tothe type elements on chain 12 and a transducer 18 magnetically coupledwith the disc. The transducer produces an output pulse each time a toothpasses the gap in the transducer. A second encoder 22 has a single slot;it generates a reset pulse each time the letter A, is in printingposition with respect to the left hand hammer. If desired, a singleencoder may be employed for generating both character position pulsesand the reset pulse in the manner shown in US. Patent No. 3,117,514.

The output of transducer 18 is coupled via an OR gate 24 to a positionencoding counter 26, which is a binary counter whose maximum count isequal to the number of characters on the chain 12. The output of encoder22, which is coupled to counter 26 via an AND gate 21, resets counter26.

The output of the counter 26 is coupled to a comparator circuit 28 whoseinput is binary encoded. input data from a suitable source 32 such as abuffer register, for example.

The output of the comparator 28 is coupled by AND gates 35 andamplifiers 36 to he operating coils of the solenoid operated printhammers 14 to the end that when the output of counter 26 matches theinput from data source 32 a selected one of the hammers 14 fires.

The hammers 14 are selected sequentially by a second counter 34,starting with the left-hand hammer in the embodiment shown andproceeding to the right a column at a time. To this end, control logiccircuit 37, which has one input coupled to the output of comparator 28,produces an output pulse each time a hammer fires; a counter 34 countsthese pulses and enables sequentially each of the AND gates 35.

In addition, control circuit 37 has an input from the data source 32 andproduces output pulse or pulses in response to certain input data suchas, for example, when a column is to be skipped.

The output of control circuit 37 is coupled via OR gate 24 to theposition counter 26 also so that the count therein advances one counteach time a hammer fires or a column is skipped. In this manner, thelogic system of this invention accounts for the fact that as the hammersare selected from left to right (for example) with the chain circulatingin the opposite direction, a particular character arrives in a printingposition one count earlier for each hammer selected.

An output from counter 34 enables gate 21 only while the first hammer 14of the print line is selected, thereby preventing counter 26 from beingreset until the last column has printed. Thusly, the count from controlcircuit 37 is cumulative during the printing of a single line.

In operation, a reset pulse from encoder 22 initially resets counter 26and an output from counter 34 enables the gate 35 associated with theleft hand hammer 14, for example. Counter 26 counts the pulses fromtransducer 18. When its output matches the binary encoded input datafrom source 32, an output from comparator 28 is coupled with theleft-hand hammer 14 via its enabled gate 36, firing this first hammer.

In response to the output from comparator 28, control circuit 37produces an output which advances both counter 34 and counter 26 onecount. At the same time, gate 21 is disenabled, preventing the resettingof counter 26 until a complete line has been printed. Thusly, the countin counter 26 corresponding to each letter of the font advances onecount to account for the fact that each letter arrives at the secondhammer one count earlier. When an entire line has been printed, gate 21is again enabled, the counter reset by a pulse from encoder 22, and theoperation is repeated.

Thus, it will be appreciated that the object of this invention has beenaccomplished. By simply advancing the position counter one count foreach printed (or skipped) column, the code in the position is maintainedin correct correspondence with the column being printed.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims. It is further obvious that various changes may be made indetails within the scope of the claims without departing from the spiritof the invention. It is, therefore, to be understood that this inventionis not to be limited to the specific details shown and described.

What is claimed is:

1. In an impact printer in which a type font moves parallel to a line ofprint hammers in one direction and in which the character columns areprinted one-at-a-time progressing in a direction opposite the directionof type font movement, a logic system comprising in combination:

first means for producing a pulse each time the font moves apre-determined distance,

a counter having an input and an output,

said counter recycling at a predetermined count which is a function ofthe number of characters in said font,

means for coupling the output pulses from said first means to the inputof said counter to advance said counter,

a comparator having at least two inputs and an output,

means for coupling the output of said counter to one input of saidcomparator,

a source of information,

means for coupling said source of information to another input of saidcomparator,

said comparator producing an output signal when there is a comparisonbetween its input signals,

means for selecting each one of the print hammers sequentially,

means responsive to the output signal of said cornparator for firing aselected one of said print hammers, and

means for coupling an input pulse to said counter to advance saidcounter one count each time a selected hammer is fired or a column isskipped.

2. A logic system for an impact printer as in claim 1 further including:

second means for generating a reset pulse each time said font completesone circulation,

means for coupling said reset pulse to said counter to reset saidcounter, and

said coupling means including means for blocking said reset pulse untila full line has been printed.

3. A logic system for an impact printer as in claim 2 wherein saidcounter recycles upon reaching a count equal to the number of typeelements on said font.

4. A logic system for an impact printer as in claim 3 wherein said typefont is mounted on a flexible belt.

References Cited UNITED STATES PATENTS 2,918,865 12/1959 Wooding 101-111X 2,993,437 1/1961 Demer et al. 3,099,206 7/1963 Hense. 3,117,514 1/1964Doersam. 3,289,576 12/ 1966 Bloom et al 10193 3,303,775 2/1967 Giannuzzi10193 3,312,174 4/ 1967 Cunningham 10193 WILLIAM B. PENN, PrimaryExaminer.

